1. Field of the Invention
The present invention relates to a regenerative refrigeration cycle apparatus having a regenerative tank, and a control method for the apparatus.
2. Description of the Related Art
In recent years, air conditioning systems having a refrigeration cycle and employing a regenerative tank have come into widespread use. The refrigeration cycle of a typical air conditioning system of this type generally comprises a variable-capacity compressor, a four-way valve, an indoor heat exchanger, a pressure reducing valve, and an outdoor heat exchanger, which are connected in succession. By switching the four-way valve to change the passage of a refrigerant, a cooling cycle or a heating cycle can be formed in succession. The regenerative tank, which includes a closed vessel, is situated between the four-way valve and the discharge side of the compressor. The vessel contains radiation-and absorption-side heat exchangers, along with a regenerative material which is subject to substantial variation in volume.
In the refrigeration cycle constructed in this manner, the heating operation takes place as follows:
Refrigerant discharged from the compressor flows successively through the radiation-side heat exchanger, the four-way valve, the indoor heat exchanger, the pressure reducing valve, the outdoor heat exchanger, and the four-way valve, and then returns to the compressor. As the refrigerant passes through the indoor heat exchanger, it condenses and releases condensation heat into a room, thereby producing a heating effect.
A regenerating operation is performed if the amount of heat accumulated in the regenerative material is reduced to a predetermined value or less, after the air conditioning system stopped for a long period of time. In this operation, the refrigerant flows in the same manner as in the heating operation, while a room fan, which is opposed to the indoor heat exchanger, is stopped. Accordingly, the refrigerant condenses only in the radiation-side heat exchanger, and not in the indoor-side heat exchanger. Thus, all the condensation heat is accumulated in the regenerative material.
The heat accumulated in the regenerative material, in this manner, is utilized for the start of the heating operation or the like. On the early morning of a cold winter day, for example, the compressor and other components of the refrigeration cycle are so cold that it takes much time to initiate the heating operation. Accordingly, heating start operation is performed in order that the heat from the regenerative material is absorbed to allow the refrigerant to be heated to a predetermined temperature in a relatively short period of time. As a result, the refrigerant discharged from the compressor flows through the radiation-side heat exchanger, four-way valve, indoor heat exchanger, and absorption-side heat exchanger, and then returns to the compressor. The refrigerant absorbs heat from the regenerative material in the absorption-side heat exchanger, thus increasing its temperature and evaporating. Thereupon, the refrigerant introduced into the compressor attains a fully high temperature despite the low outside air temperature, so that the heating effect can be obtained in a very short time after the start of the operation of the refrigeration cycle.
The heat accumulated in the regenerative material is also utilized in defrosting operation for defrosting the outdoor heat exchanger.
Constructed in this manner, however, the regenerative refrigeration cycle is subject to the following drawbacks.
In the regenerating operation, heat is accumulated in the regenerative material by condensing the refrigerant only in the radiation-side heat exchanger in the regenerative material. The condensation capacity of the radiation-side heat exchanger is much smaller than that of the indoor heat exchanger, and the condensation heat released from the former is less. Therefore, the efficiency of the regenerating operation is lower. Moreover, the radiation-side heat exchanger cannot fully condense the refrigerant by itself, so that the refrigerant is not fully condensed when it circulates through the refrigeration cycle. Therefore, the pressure on the suction side of the compressor increases at once to a high level. Accordingly, a high-pressure protection switch or protective control circuit of the refrigeration cycle is actuated so frequently that the compressor is started and stopped repeatedly. In consequence, the temperature of the refrigerant discharged from the compressor fails to be high enough, so that the regeneration temperature of the regenerative material is lowered, thus entailing the reduction of the efficiency of the regenerating operation.